EV range boost from 'invisible' solar roof

September 05, 2019 //By Christoph Hammerschmidt
The Fraunhofer Institute for Solar Energy Systems ISE has developed a car solar roof with solar cells attached under a layer of paint, making them invisible.
The Fraunhofer Institute for Solar Energy Systems ISE has developed a car solar roof with solar cells attached under a layer of paint, making them invisible.

The roof can be individually coated in any colour, with the solar cells invisibly integrated into the pre-formed solar roof. With a rated output of around 210 W/m², the roof can supply electricity for around 10 km on a sunny day for a mid-range electric car. Projected over a year, Fraunhofer ISE assumes that "the vehicle's range can be extended by about 10 percent" - or that electricity consumption for the same distance travelled will fall accordingly.

The calculation is based on the unshaded solar radiation at the ISE site in Freiburg im Breisgau (one of the sunniest cities in Germany). In addition, the consumption of the electric car was based on 17 kWh per 100 km and an annual mileage of 15,000 km. Institute director Andreas Brett assumes that in the course of decarbonizing energy generation, solar cells will be integrated even more strongly into the environment in the future, at least as far as they are designed by humans. Cars are also suitable for the installation of solar cells, Brett said.

To ensure that as much of the roof surface as possible can be used, the developers have minimized the distances between the cells. The scientists are relying on what is known as shingle nesting. Similar to a house roof, the silicon solar cells are arranged overlapping, but in this case they are connected with a conductive adhesive. This should not only lead to a higher energy yield, but also result in an aesthetic overall picture.

In contrast to the solar cells previously used in cars, the special feature is that the cells are virtually invisible - they are completely concealed by an individual color coating. "The color possibilities are almost infinite," says Martin Heinrich, head of PV for Mobility at Fraunhofer ISE. The loss in efficiency is said to be only 7%.

More information:  https://www.ise.fraunhofer.de/en.html 

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